In times of old, we weren't as efficient at disposing bodies as we are now, so monks and priests were sometimes forced to get a little creative when their churches' graveyards and catacombs ran out of room.
The pictures below aren't of satanic cults or the recording studios of Norweigan death metal bands. They are actually just the aesthetic choice of some regular churches needed to get creative with where they buried their dead.
It seems wrong that these churches are using human bones, but they are actually honoring anyone who is included in the structures. They will forever be a part of this big, beautiful building. It's just as inspiring as it is insanely creepy.